Meaning of A5 in English

A5

A5 /ˌeɪ ˈfaɪv◂/ BrE AmE noun [uncountable]

a standard size of paper, used in Europe and Japan. A5 paper measures 148 x 210 ↑ millimetre s ⇨ A3 , A4

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.